Mixing of acid and base pretreated corncobs for improved production of reducing sugars and reduction in water use during neutralization

Pretreatment of biomass for bioethanol production makes it necessary to use large amounts of water for removing inhibitors and neutralization. In order to reduce water usage, separate batches of corncobs were hydrolyzed in 1 M NaOH and 0.05 M H2SO4, respectively, and the hydrolysis products were mixed to achieve a pH of 7. This approach lowered water usage by 10-fold compared with neutralization by distilled and recycling wash water. Mixing of the pretreated biomasses (121 °C, 20 min) increased release of reducing sugars during enzymatic hydrolysis with cellulases (38.49 FPU(IU)) produced by Phanerochaete chrysosporium NCIM 1106 by 2- and 15-fold compared with the sugars released from the unmixed NaOH- and H2SO4-treated corncobs, respectively. Enzymatic hydrolysis (EH, cell free extract) of the mixed material released 395.15 mg/ml of sugars during 48 h, slightly less than what was achieved by microbial hydrolysis (whole cell hydrolysis), 424.50 mg after 120 h.